Many Flickr group's administrators as a rule of membership want to copy and past a signature (often with a picture) to show that photo has been seen inside the group stream, to prove their group is alive and fruitful. But the other reason that drives that administator's way of doing, is a mere spot question. Nicer advertisement picture, more clicks and visits to the group.
FlickrReferComment - a useful Greasemonkey plugin created by Pierre Andrews - automatically shows where the picture has been seen. And also with probing precision:
The "proof" is there, but where are those appealing little sticky pictures? My contribution to that code is my OurOwnSignature feature (and since then many others too). It lets to automatically add a custom signature, right the one chosen by group administrators, when you come from a group stream. Everything automatically.
No need of any boring and time wasting "copy-and-pastings".
